tests/test-install.t

backout: avoid redundant message examination

Before this patch, "hg backout" examines "--message" and "--logfile"
options explicitly.

But this examination is redundant, because "commitfunc()" can receive
the result of same examination by "cmdutil.logmessage()" in
"cmdutil.commit()" through "message" argument.

This patch avoids redundant message examination by "message"
examination in "commitfunc()".

hg debuginstall
  $ hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob)
  checking Python lib (*lib*)... (glob)
  checking installed modules (*mercurial)... (glob)
  checking templates (*mercurial?templates)... (glob)
  checking commit editor...
  checking username...
  no problems detected

hg debuginstall with no username
  $ HGUSER= hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob)
  checking Python lib (*lib*)... (glob)
  checking installed modules (*mercurial)... (glob)
  checking templates (*mercurial?templates)... (glob)
  checking commit editor...
  checking username...
   no username supplied
   (specify a username in your configuration file)
  1 problems detected, please check your install!
  [1]